A device for detecting a combustion-chamber pressure in a diesel engine is described in German Patent No. DE 196 80 912, the device having a pressure sensor and a heating section of a glow plug. This heating section faces an interior of a cylinder of the diesel engine and is able to be acted upon by the combustion-chamber pressure. A fixation element fixes the heating section in place inside a housing of the glow plug. The pressure sensor is disposed between this fixation element and the heating section.
In this system the heating section embodied as a heating pin, and the pressure sensor is braced by the same fixation member with respect to the housing of the glow plug, so that the pressure sensor is acted upon by at least approximately the entire force acting on the heating pin. With certain sensor materials this has the disadvantageous result that the pressure sensor is also operated in its non-linear region, which leads to a non-reproducible measuring signal and an unreliable detection of the combustion-chamber pressure in the internal combustion engine.
Furthermore, the afore-described placement of the pressure sensor with its spatial proximity to the interior of the cylinder and its direct coupling to the heating pin during operation of the diesel engine has the disadvantage of entailing considerable thermal loading for the pressure sensor, so that it is at risk with regard to its operating reliability. In particular when the signal emission of the pressure sensor becomes unstable due to fluctuations between high and low operating temperatures, this may lead to malfunctions of the device for detecting the combustion-chamber pressure in the internal combustion engine, and thus also to an unreliable detection of the combustion-chamber pressure in the internal combustion engine.